In After Effects CS5.5 Adobe finally answered one highly requested feature: allow older versions of AE to open new project files. Sounds great right? Not really, they allowed you to open CS5.5 files in CS5 but not any version older then that.

Fear not, Paul Tuersley created Open Sesame, a custom plugin that allows you to save out Projects files that can be opened all the way to back to CS3!

Here’s how it works:

Open the project you want to convert, run OpenSesame and click Export Project. A log file will be created listing any items that can’t be exported. If you don’t have the version of After Effects required to open the project you should get the person who created it to complete the first step using OpenSesame, then send you the exported text file.
Launch the earlier version of After Effects (CS3 or later) and run OpenSesame. Click Import Project, then choose the exported OS project file.

But this plugin isn’t a magic bullet.

The following features aren’t currently supported:

Paint, Rotobrush and Puppet Pin effects.

Text style support is CS4+ only and doesn’t include features like kerning, vertical and paragraph text, or multiple text styles on one layer.
Proxies.

Custom data values. Effect properties with custom data values can’t be exported, such as the Levels Histogram and the Hue/Saturation effect. In these cases you could use the Levels (Individual Controls) and Color Balance (HLS) effects instead.

I don't care about using an older version of AE to open newer files. Exactly the opposite. WHAT are you supposed to do when the current version of AE informs you that it can't convert the file and you should "use an older version of AE and resave" to do it?? 1, I don't have the older version, those files were created almost a decade ago, and 2, what good would it do to "resave" it with the SAME older version??